Fibronectin mediates normal attachment of cells. It is often absent on the surface of malignant cells, and this may be related to their capacity to grow invasively and metastasize. The aim of this proposal is to study the molecular events involved in the deposition of fibronectin to extracellular matrix, in its mediation of attachment of normal cells, and in the disturbance of these two processes in malignant cells. Fragments of fibronectin will be generated by enzymatic treatment, and they will be studied with respect to the various biological activities of the whole molecule. These activities include binding to collagen, fibrin(ogen), glycosaminoglycans, and mediation of cell attachment. Fragments that have retained biological activities will be purified to homogeneity and characterized immunochemically and chemically. The significance of the interactions of fibronectin with other macromolecules and with cell surfaces to the deposition of fibronectin into an insoluble matrix will be studied by determining which fragments have retained the capacity to become incorporated into extracellular matrix in cell cultures. The cell surface molecule(s) that interact with fibronectin to cause binding of cells to fibronectin matrices will be isolated and characterized. Naturally occurring fibronectin fragments, identified in urine in preliminary experiments, will be isolated and characterized as described above. Assays specific for the fragments will be developed to allow exploration of the possibility that the amount of these fragments in urine might serve as an indicator of degradation of extracellular matrix and basement membranes by tumors. These studies will be helpful in increasing understanding of the biological behavior of tumor cells, including metastasis, at a molecular level.